The present invention relates to an AC line filter, and more particularly to an EMI preventive AC line filter which is space-saving, and can effectively eliminate electromagnetic interference.
FIGS. 1 and 2 show an AC line filter according to the prior art. This structure of AC line filter is comprised of a cylindrical winding holder formed of two symmetrical halves 50, a rectangular iron core formed of two substantially U-shaped symmetrical halves 4, and a rack 6. The symmetrical halves 50 of the cylindrical winding holder each comprise a plurality of partition grooves 52, a plurality of winding grooves 51 separated by the partition grooves 52, a toothed portion 53 at one end, and an axially extended coupling groove 54 of semi-circular cross section. By means of the axially extended coupling grooves 54, the symmetrical halves 50 of the cylindrical winding holder can be attached to the fixed shaft of a winding machine, enabling the toothed portions 53 of the symmetrical halves 50 of the cylindrical winding holder to be set into engagement with the driving mechanism of the winding machine, so that enable wires can be automatically wind round the winding grooves 51. The two symmetrical halves 4 of the iron core are fastened together and coupled to the winding assembly of the cylindrical winding holder, and installed in the rack 6. The rack 6 comprises a longitudinal coupling groove 61, which receives the symmetrical halves 4 of the iron core, symmetrical support arms 63 disposed at two opposite sides of the longitudinal coupling groove 61, which support the cylindrical winding holder in place, and two partition blocks 62 disposed at two opposite sides of the longitudinal coupling groove 61 on the middle, the partition blocks 62 each having a plurality of ribs 621 respectively engaged into the partition grooves 52 at the symmetrical halves 50 of the cylindrical winding holder. This structure of AC line filter is still not satisfactory in function. Because the axially extended coupling grooves 54 of the symmetrical halves 50 of the cylindrical winding holder are not tightly matched with the symmetrical halves 4 of the iron core, a magnetic resistance is produced in gaps in the axially extended coupling grooves 54 around the symmetrical halves 4 of the iron core, causing the filtration effect of the EMI preventive AC line filter to be affected. Further, because of the design of the partition grooves 52 at the symmetrical halves 50 of the cylindrical winding holder, the space for the winding grooves 51 is relatively reduced. In order to provide sufficient space for the winding grooves 51, the size of the cylindrical winding holder must be relatively increased.